Experimental Study On Mechanism Of Two-layer-composition Bank Failure

The bank failure is a quite prevalent and prominent geologic hazard along themiddle-downstream Yangtze River,which occurred more frequently. Bank failure and itsprevention is a very important issue in the river development and governance areas.However,thestudy on the mechanisms of bank failure are still immaturity,which are almost based on certainexamples by analyzing and empirically summarizing and are parlous lack of lab and field teststudies. Therefore，the study on the mechanism of bank failure，especially the study on theclassification and the influence factors of bank failure，should be reinforced to obtain the causesand the laws of development of bank failure，which have imponderable value for the floodcontrol and disaster mitigation.Based on the collecting and analyzing the former research results and large-scale labmodel test,different classifications of bank failure are summarized,the mechanism of bank failureare preliminary studied.Main conclusions are listed as follow:1. Different forms of bank erosion and failures in U.S.Mississippi and inmiddle-downstream Yangtze River and their features are reviewed more comprehensively.2.As the various influence factors of bank failure,the paper summarizes the factors from amacro and investigates its features.3.Via the large-scale lab model test,the study on common phenomena of bank failure andits main influencing factors is conducted.Main conclusions are as follows:(1)The different forms of bank failure under hydrostatic conditions is mainly failure type ofbank failure.However, there are several forms of slliding failure,sinking failure and falling(shearand toppling) under hydrodynamic conditions.(2)As the increase of the riverside slope and the ratio of the lower to upper and the instreamflow,the bank failure is more proned to happen and the scale is larger.Bank will seriously fail atthe inner of the upstream,apex and the outer of the downstream in curved reach,of which there isa greater erosion rate at the apex.(3)The change process of the water level has effect on bank failure.When the water levelrises,bank failures slowly and always in the form of sliding failure.But the possibility of the bankfailure will increase in the water level falling process.4.The different types of ecological revetment works in the middle and lower reaches ofYangtze River are toe ecological protection and slope ecological protection.